REDUCTION OF THE INRUSH CURRENTS OF THREE-PHASE POWER TRANSFORMERS

Abstract

Inrush currents that occur during the energization of a three-phase power transformer can reach very high values and cause many problems in an power system. A mathematical model of a transformer has been developed for the investigation of this problem, taking into account the effects of saturation, hysteresis and remanent magnetic flux. An algorithm has been described for the determination of the optimal instant of energization, with the goal of reducing inrush currents. As a method for measuring remanent magnetic flux, integration of the secondary voltage during the previous deenergization is proposed. A circuit model has been prepared of a system for the controlled energization of a three-phase transformer in which the simulation results are confirmed by measurement.